Such a mechanism is provided with a screw having an external thread, with a nut arranged around the screw and having an internal thread, and with a plurality of longitudinal rollers engaging the external and internal threads of the screw and of the nut. Compared to a ball screw mechanism, the main advantage of a roller screw mechanism is increased admissible load capacities.
One type of roller screw mechanism includes rollers having an external thread engaging the external and internal threads of the screw and of the nut. The threads of the rollers and the thread of the nut have helix angles that are identical to each other and different to that of the thread of the screw such that, when the screw rotates in relation to the nut, the rollers rotate on themselves and roll about the screw without moving axially inside the nut. The rollers are rotationally guided parallel with the axis of the screw by teeth added on the nut and engaging teeth of the rollers. Such a mechanism is called a planetary roller screw.
With the current design of roller screw mechanisms, the teeth of the rollers and of the nut have, in cross section, an involute profile.
Furthermore, the teeth are threaded during the threading step of the rollers. During the meshing of the teeth of the rollers with the teeth of the nut, the pressure is increased at the top of the teeth due to thread on the teeth of the rollers. This increases the wear of the nut, which has to be replaced.
One solution to solve this problem is to increase the hardness of the nut. However, boring holes in the nut will become very difficult.
The aim of the present invention is to overcome these disadvantages.
More particularly, the aim of the present invention is to provide a roller screw mechanism wherein, for a given diameter, the load capacity is increased.